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<title>Species with Zero Concentration</title>
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<h3>Dissolved species with zero concentration</h3>

<p>Some chemical species need a special treatment:</p>
<ul>
<li><nobr>&#147;e&#8722;&#148;</nobr> and <a href="ChEq_H2O.htm">water</a> <nobr>(H<sub>2</sub>O)</nobr></li>
<li><a href="ChEq_Gases.htm">Gases</a></li>
<li>Species with a <a href="SP_Removing_Species.htm">name beginning with
  										<nobr>&#147;*&#148;</a></nobr></li>
</ul>

<p>For these species the concentration must be set to zero (although their
<a href="SP_Activity.htm">activity</a> may be calculated).</p>

<p>For <b>electrons</b> it is possible to plot&nbsp; <nobr>log{e&#8722;}</nobr>
<nobr>(= &#8722; <a href="1_Eh_pe.htm">pe</a>),</nobr> but the concentration of
<nobr>&#147;free</nobr> <nobr>electrons&#148;</nobr> will not appear in a
fraction or logarithmic diagram. Note that the <i>total</i> concentration of e&#8722;
may be given in the input, see for example the data file <nobr><tt>EX5.DAT</tt>.</nobr></p>

<p>For <b>water</b> <nobr>(H<sub>2</sub>O)</nobr> it is not possible to give a
total concentration.</p>

<p><b><a href="ChEq_Gases.htm">Gases:</a></b> only aqueous species and solids
are considered when making a diagram, and the concentration (in mol/L) for gases
is set to zero. The <i>fugacity</i> <nobr>(&#8776;</nobr> partial pressure) is calculated and
it is displayed in <nobr>&#147;log activity&#148;</nobr> diagrams
(<a href="S_Diagr_Loga_CO2.htm">example</a>).</p>

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